JFHQ-NCR's area of responsible includes the District of Columbia and neighboring counties and cities of Maryland and Virginia. JFHQ-NCR draws together the existing resources of the Army, Navy, Air Force, Marine Corps, Coast Guard and NORAD into a single point headquarters for planning, coordination and execution of the mission in the National Capital Region.

The National Capital Region is the political and military center of gravity of the U.S. with an infrastructure vital to the global interests of the nation. Many federal, state and local agencies are located here, in addition to a large number of foreign embassies and other international organizations toward which the U.S. has security responsibilities. JFHQ-NCR supports U.S. Northern Command (USNORTHCOM) in the timely execution of its mission by coordinating all operational military service elements at the seat of government.

The organization is prepared to respond cooperatively with other federal agencies or civilian authorities should they be called on for homeland defense or civil support needs.

During incidents of national significance, JFHQ-NCR transitions to Joint Task Force National Capital Region (JTF-NCR). JTF-NCR brings appropriate levels of military support to bear in the National Capital Region when authorized by proper authorities or as immediately required to save lives, prevent human suffering or mitigate great property damage. Such support, primarily land-based, will be under the command and control of the joint force commander.

Support may be in response to planned events, such as security support during a presidential inauguration, or in response to natural disasters or terrorist attack. After the response, JTF-NCR stands down and redeploys response assets.

Operating through JFHQ-NCR, USNORTHCOM coordinates support efforts, as well as the air, land and maritime defense of the National Capital Region, under the command and control of the joint force commander. USNORTHCOM is the combatant command established in 2002 to provide command and control of Department of Defense (DOD) homeland defense efforts and to coordinate defense support of civil authorities.

JFHQ-NCR operates within the scope of the law. It will not engage in direct law enforcement activities, but when requested by civil authorities and approved by the civilian leadership of DOD, it supports civil authorities in their public safety missions. Existence of a JFHQ enables better planning by all parties, to the benefit of the public.